Light sucking flames look like magic 

There's so much more I could say about EnChroma but it's already 19 minutes long! The sponsor is Odoo. Try it for yourself today: www.odoo.com/r/kYo

7:40 Hey! There's a legit use case for that! People who live near sodium public lighting might want their windows tinted like that, so their room is dark during the night but then in the morning (most) sunlight will filter through and help them gradually wake up!

Now someone can make the REAL Darksaber!

I see this flame and the first thing that comes to mind is the Godskin Cult.

15:22 is something that I didn't expect to see, but I was glad it was there.

I don't know whether it's the quality of your pedagogy or if we just happen to think alike but whenever I have questions while watching one of your videos you inevitably say, "You might be wondering..." and then answer those questions. It makes your content extremely satisfying to watch. The downside is that since I'm left with no outstanding questions I rarely comment, hurting that elusive "engagement" metric. So here's me making up for that.

When I was learning electronics in the Navy, we used to joke that DS label used for lights in a circuit diagram stood for Dark Sucker. When a bulb blows, all the dark leaks out.

Here in Sweden, I miss the highway sodium lights upon startup (I remember them shifting from purple/blue/yellow/deep red/orange to the final yellow light). A late summer evening with a clear, rather dark sky, seeing the sodiums start up into the distance... awesome.

Posting for everyone else who doesn't have patience - he doesnt have the camera set to full color (natural color), he's disabled auto white balancing on the camera, and he's shining an incredibly bright sodium street light on the scene.

i have struggled with "Spin" of subatomic particles for years. The "it tells us which way the moving electric charge points its magnetic field" line felt like an epiphany i have waited decades for

Sodium street lamps were actually way better at controlling light pollution. Because they emit light at such a narrow spectrum, it was possible to make something called a CLS (City Light Suppression) filter that removes the sodium band, but even wearing those glass blower glasses would mean you could actually see the stars, and through a telescope nebula, and galaxies quite well, almost as though you were in a dark sky site with no city lights. The LED bulbs everyone is switching to are horrible because they emit white or blue light broadly, making it almost impossible to filter. Further, these colors also increase the light dome (basically how far light travels away from it's source) over urban areas, meaning that areas around cities that were once dark no longer are. This has forced backyard astrophotographers to switch to narrowband imaging, which is really only useful for nebula, and that's incredibly expensive to get into. To make up for this, some companies sell sodium-like LED street lamps for locations where having dark skies are important, but they are very expensive (basically they are taking advantage of the situation). Personally, I wish we'd just switch back to the sodium lamps, they are as efficient as LED's and they're just better for the night time environment.

Thanks for all the neat videos over the years Steve!

I saw a misconception in this video which keeps getting spread, mainly because the actual explanation is a lot trickier and weirder to understand than the actual reasoning. In the video, Steve says that the reason there are two lines is because the electron spins are either in the same direction or different direction from the orbital angular momentum. But, this is not true. Rather, it is because of statistics and the Pauli exclusion principle. The Pauli exclusion principle says that an electron cannot be in the same quantum state as other particles. As it turns out, there are 4 different options for spin orientation: both spinning in the same direction upwards, both spinning in the same direction downwards, one spin up and the other spin down, and then vice versa. We then write these as a math statement. The first one is written as ↑↑, the second is ↓↓, the third is ↑↓, and the last is ↓↑. HOWEVER, as it turns out, ↑↓ and ↓↑ are not actual "good" states. For those who this word means something to, they aren't eigenvectors of a 2x2 matrix -- which is necessary for a state to be physically possible. So the solution is to change the set of states we work with to: {↑↑, ↓↓, ↑↓+↓↑, ↑↓-↓↑}. This is the set of all possible spin states. Now onto the Pauli exclusion principle. Because an electron is a "fermion," when you swap two electrons, all that should change is the overall quantum function -- the thing which describes the electron -- should have a negative sign. Let s be the spin state, and p be the rest of the function -- describing which orbital the electron is in. We write that the whole function P is a function of particle 1 and 2, written as P(1,2) and equaling s(1,2)*p(1,2). In other words, P(1,2)=s(1,2)*p(1,2), with * just meaning multiplication. The "fermion" statement I made means P(2,1) = -P(1,2). So, s(2,1)*p(2,1) = -s(1,2)*p(1,2). Now, we will look at each of the spin states. Note that when you swap the order of the first three spin states, we get ↑↑, ↓↓, ↓↑+↑↓. The last is identical to ↑↓+↓↑ because you can swap the order of addition. HOWEVER, the last state becomes ↓↑-↑↓ = -(↑↓-↓↑). This means if the particle is in the first three states, then we have to say p(2,1) = -p(1,2), and if the particle is in the last state, p(2,1) = p(1,2). This property is what causes the electron to have different energy levels. If the particle has the first property p(2,1) = -p(1,2), the particles tend to be repelled away from each other, and we say that the position function has a "fermionic" behavior. In fact, THIS is why solids are solid. It's not that there are electromagnetic forces repelling electrons from electrons. Rather, it's because of this fermionic behavior of matter. Neutrons do the SAME exact thing, which is why neutron stars are a thing. They are held together and kept from collapsing by this pressure called "degeneracy pressure," despite having a neutral charge. If a particle has the second property, p(2,1) = p(1,2), the particles tend to be attracted towards each other, and we say that the position function has a "bosonic" behavior. Light is a boson. A bosonic particle tends to be attracted to other of the same type. I will make an important distinction: the repulsion of fermions and the attraction of bosons ONLY happens because the particles are EXACTLY the same. All electrons are 100% completely indistinguishable, there is no way to know for 100% certain one electron is not another electron or one photon is not another photon. Fermions are ONLY repelled from other fermions for which they are 100% absolutely identical to, and bosons are ONLY repelled from other bosons they are 100% absolutely identical to. Protons, neutrons, and electrons, for example, are not repelled from each other by this degeneracy pressure. FINALLY we can get into why the energy levels are different. If they are in the fermionic position state, we call this state the "triplet" state, and the position function needs to be of a higher energy because of the degeneracy pressure pushing the electron further away. And, if they are in the bosonic position function, we call this state the "singlet" state, and the position function needs to be of a lower energy level. Now, I will admit, I feel like there is something slightly wrong here. I believe an important statement is I need to say magnetic fields show up someplace in here because iirc, splitting of the singlet and triplet state don't occur unless if there is a magnetic field. Iirc, this magnetic field is due to the nucleus's spin (?). I am willing to correct myself if I made any mistakes. At the very least, the misconception which keeps getting spread is that objects are solid because of electromagnetism, which isn't true; it's because of spin statistics.

2:30 I like how your camera can't even remotely pick up on the actual rainbow in that diffraction grating, and just gives you three bands of RGB.

Someone else may have already commented about this, but the fact that the light emitted by sodium atoms produces roughly one wavelength of visible light was used in movies for compositing in lieu of greenscreen. This technique known as "Sodium Vapor Process" or informally "Yellow screen" utilized custom-made beam-splitter prisms with embedded notch filters (similar to how EnMouldia glasses work) and Bandpass filters split the image into two parts to create a perfect matte. This process was famously used by Disney in the filming of Bed knobs and Broomsticks as well as Mary Poppins.

Very nicely done, good explanation of subatomic photon production (and absorption). As a theoretical concept, I had thought about "dark light", but had never seen an example of such as being demonstrated via a black flame. Of course, there are well known examples of "invisible" flames (partially a function of the flame temp, and the relative energy levels of the electron orbits), a terrifying example of which is the methanol fuel used in race cars. It has happened when a driver is being burned with a flame no one can see, but the process of being burned becomes extremely apparent.

This video is amazing. Your casual explanation of spin to get to the why of the double lines emmiting form sodium was marvelous, I love when I get answers to questions I didn't know I have. And I'm totally using that orbit analogy to explain this. Thx for your content, cheers Steve

16:12 From one uncle to another, this is top notch uncling giving your nephew's RU-vid a shoutout. Bravo.

I'm really glad you specifically mentioned that color blindness is due to the L and M cones overlapping more than usual! Lots of people seem to think that color blindness is caused by a lack of one or the other, when really it's a mutation. That said, the reason why the literature is inconclusive is largely because there are multiple types and degrees of color blindness. "Red-Green" color blindness is actually a catch-all for the two most common categories: Protan (mutated L ('red') cones), and Deutan (mutated M ('green') cones). Each of those two categories additionally has 'full color blindness' variants: Protanopia (when L cones are mutated to the extent that they behave exactly like M cones), and Deuteranopia (when M cones are mutated to the extent that they behave exactly like L cones). Whenever the mutation doesn't cause them to act _completely_ like the other type, it's called _anomalous trichromacy_, and there are various degrees to that. The terms used are: Protanomaly (when L cones have shifted to behave somewhat like M cones), and Deuteranomaly (when M cones have shifted to behave somewhat like L cones). So, because of all those different types, the way that light filtered by the Enchroma glasses is perceived will differ depending on which type of color blindness a person actually has. Notably, they can *only* work for people with anomalous trichromacy, and it will work better with one type of anomalous trichromacy than the other (though I don't know which one it works better for). People with dichromacy (full color blindness) would have no use for them, and not be able to see any difference. And finally, people with tritanopia and tritanomaly are left without any options because it's already super rare anyway. The only time I've ever even seen a joke or mention of it in something that's well-known, is a subtle jab at tritanopia in the movie 'A Christmas Story', when the father can't tell the difference between the green and blue lights. I've been studying color blindness for several years now, and it was only this past Christmas while watching that movie yet again that I caught that and it made me burst out laughing in front of my suddenly very confused family.

This is incredible experiment. I love how you can find all these paradoxical effects in usual things. You are the best!

Rarely learnt so much in such a short time! Especially the amazing , lucid explanation of the two lines and electron spin. My thanks :)

"because id be dead" got me spitting out water lmao

imagine getting your youtube channel advertised by your uncle Steve Mould, what a move!

A pleasure to watch and learn from you, Steve. Great pacing, great level of depth vs expedience. Subscribed

Back in the early 1980s, after I acquired my driver's licence, I ran a red light on a section of roadway lit by sodium street-lighting because I happened to approach the lights after they'd turned to amber, perfectly camouflaged amongst the sodium lights. Fortunately there were no other vehicles around as it was very early in the morning!

A fun fact about the sodium light spectrum is Disney created a special process back in the day that worked better than any blue/green screen using a prism. They could get much more detail around a subject without any spill from the screens as well as being able to film sheer & transparent materials. Marry Poppins is the best example of this. The Corridor channel did an interesting deep dive and recreated the effect on one of their channels.

Best line: "Its a weirdly polarized topic now and I don't like being shouted at."

hey steve,i really love you're videos. So, recently i stumbled upon this video where something strange happens when dry ice is put into gasoline. I thought you might wanna look into it.Keep up the great work!!

This is fascinating! Your transition was so clever that I even watched your promo. 😀

The CRI of low-pressure sodium lamps is not just low, not just 0, it is actually Negative. It is so wonderfully efficient at both illuminating as well as destroying any colour recognition.

About a decade ago, my wife and I were visiting Killarney, Ireland. While we were walking back from the town center to our B&B after sunset one night, we noticed that her bright red raincoat appeared a very dark gray under the streetlights. Turns out, this was the first time we had encountered sodium streetlights in person.

10:58 Thank you for the best explanation of electron spin I've ever encountered!

Vids keep getting better, Steve. Thanks for the great content!

PRACTICAL APPLICATION: I design optics for street lights. With respect to high pressure sodium lamps, we had to make sure our optics did not reflect light back into the arc tube because the sodium would absorb its own light and cause the arc tube to overheat. This would shorten the life of the lamp.

You might not like being shouted at, but how about some praise? I highly appreciate you doing resarch into the glasses before shouting them out in any way, even more so that you actually share the controversy, instead of just saying it's bs or 100% fact. That's exactly what I want out of a science channel!

What a great video. Very clear explanations of things that have confused me for ages!

Love how you jump topics and cover so many interesting things in this one video!

Sodium light again huh..? first the disney 'greenscreening' prism, now black flames! Sodium light is very useful for color spectrum science it seems.

Was that a hidden richard butt in the colorblind test? lol

The irrepressible science nerd in me loves your very detailed explanations of natural phenomena, but I also appreciate that you manage to keep it all very coherent and entirely comprehensible. Thank you for this fascinating and instructive video, and for this lovely channel, which I am very happy to have discovered. 🙏

This video was such a good use of my time -thanks for making it!

15:07 "It's a weirdly **polarized** topic now..." * puts the sunglasses on as a the Who song starts blasting *

I can't believe Steve slipped Dickbutt into a colorblindness dot test 💀

Really good explanation. I do LOVE it. THX for this!

Superb concise explanation for what we see.

I have the immense joy of being incredibly colorblind. The enChroma glasses did not work for me. However, for $30, I found a particular shade of polarized dark brown cataract sunglasses at CVS (a large chain pharmacy/chemist in the US, for those unfamiliar), which allow me to interpret reds far more easily than I otherwise can. It makes being outside very pleasant, and it's honestly really cool to be able to see the things people have been pointing out all my life that I never understood the interest over. It's a very noticeably subtractive experience, but I find my brain can easily ignore that aspect of it, especially after a few minutes of adaptation, and I get to experience the world slightly darker, and can notice red and red-adjacent things.

15:22 Dammit, Steve. I can't believe you've done this. By the way, your description of spin & quantized angular momentum was one of the most interesting one's I've encountered. I'm definitely going to have to keep coming back and rewatching that segment to wrap my head around it.

loved everything about this video. Thank you sr.

Wow, came here for a black flame (which I knew would be about sodium absorption lines) and learned about glass blowing, colour blindness and - finally - a good explanation of an electron spin.

"I wouldn't see that dip if I was doing this experiment in the vacuum of space - because I'd be dead." That had me rolling

As someone with mild red-green colorblindness and a pair of Enchromas, I feel like I should say that they do work, but not to allow me to "see colors I couldn't see before" Mostly what they do is allow me to distinguish shades of green and red that my eyes have trouble picking apart from the background by cutting out the duller shades of those colors and making them more vibrant. Like, say, a green bush full of red flowers. Without Enchromas I might be able to tell that there are red flowers, but unless I got up close to the bush and searched for them, I wouldn't be able to just distinguish the red flowers at a glance. My Enchromas allow me to do just that. And the same goes for different shades of green. I could physically see those colors already, my eyes just sucked at picking them out from each other when they're all mixed up. Kinda like the colorblindness tests with the different colored dots. They do make blues a bit purpley, though.

The bit about electron spin and emission lines was brilliant, thanks!

I didn't expect to hear about electron spin in this video but I am glad you talked about it. I have been unsatisfied by the lack of depth I've seen people get into on what electron spin really is. This is the first time I've heard anyone say that there is a relationship between the spin of the electron and the direction of the orbit. I was missing any sort of explanation on how the spin could be one of only two possible values, but now this gives me some idea on how that could be the case. Thank you very much for that.

Those old street lights are nostalgic af... All the memories of being driven back home from visiting family, late at night and falling asleep to the sound of the moving car and the atmosphere created by those old street lights. 🌃

I'm colorblind and have a pair of Enchromas. They do make it much easier to distinguish reds and greens, but they're not magic and I certainly don't see "new colors" I couldn't see before, although my colorblindness is not that severe either so I won't discount other people's experiences. But the best demonstration I've been able to find of their effectiveness is rose bushes. For the most common types of red-green colorblindness, the red polka dots on a green background look that rose bushes have is especially problematic. From any sort of distance away, the roses lose their definition and start to just look like darker parts of the bush. But with the Enchromas, they pop out really strongly from the bush, even from quite a distance. So it's not so much that they help you to see new colors, as much as they improve your ability to distinguish and apreciate colors you could always see. It's not like (most) colorblind people can't see red or green at all, it's just a lot harder to distinguish them from each other in most situations. Additionally, for all people (including normal-sighted people) they generally improve contrast and make all colors seem a bit more vibrant. I'm almost surprised that they haven't caught on as a luxury glasses brand just for the way they make everything look "more vibrant than real life". Although, that effect is really only true in especially good lighting.

This is a truly exceptional science video 😍 I will be sharing with all of my university-level students, and academic colleagues, and anyone else I can encourage to watch it!

Electron spectroscopy was hard for me to wrap my head around in school. Your explanation and demonstration helped the concept to finally click!

Back in my physics days, you could look up all of these lines and transitions in textbooks. Or on NIST, but that page seems to be strugging. I did the looking up for you: The 819nm transition is a 3d-3p transition. The other ones are from higher orbitals, 5s-3p for 616nm and 4d-3p for 569nm.

I always learn something when I come to Steve's channel - I love that! Very interesting stuff in this one, indeed.

Very well made video and highly interesting. Well done!

How to make blackflame: Step 1: Touch random paintings until one of them sucks you in Step 2: Fight a nun dual-wielding scythes to the death

15:23 I see what you did there 😂

This is some quality content thanks Steve!

One of your better videos for sure! Thanks for posting.

About the enchroma glasses, a youtuber "megalag" made a few episodes exposing the whole color correction glasses industry, you might find it interesting

Corridor Crew also did a video where they used a set of sodium lights to essentially re-create vfx similar to what was done on films like Marry Poppins. It involved an interesting camera set up, but resulted in a more defined chroma-keying to where you don't have to worry about other colors bleeding into the void.

I (from Australia) had glasses similar to the EnChroma ones back in 2004/2005 and they seemed to work for my red/green colourblindness they cost about $1000 at the time. I do recall specifically red being much brighter and greens being much darker the complete opposite of what I saw without them. They were sunglasses and the design went to great lengths to ensure a minimal amount of light could get in around the lenses, there was minimal gap around the frame between my face. Which became painfully obvious when someone hit me in the face with some text books and the frame of the glasses pierced my skin around my eye socket requiring a few stitches. The lenses themselves were also reflective with a mirror like effect on the outside.

That was freaking awesome! I know that Poppy keeps morphing genres... but I think this song depicts her best genre. I love it. Even the David Draiman nod.

Your dry humour never ceases to make me laugh, loved the clever joke at 12:31

I wish we still used sodium streetlights, the modern streetlights are far too bright, it doesn't feel like night-time at all. I wondered why night-time actually felt like night time as a kid, it was because of the street lights.

I love the old sodium lamps so much that I have a 35W one in my living room. My eyes have gotten so used to the monochromatic glow that I can now easily distinguish colours under it. It’s like a superpower for a sepia-tone world!

I got a pair of enchroma glasses a while back and I would agree with what Steve said in both cases. I am red-green colourblind and when I tried to crack the Ishihara test after using them, I did not have any improvement in my test scores. Having said that, the richness of a grass field or a bouquet of roses is lost on me but when I use those glasses, these look really vibrant. The closed bud hibiscus plant has these finger like red flowers in a sea of green foliage and I could never even spot these flowers on the plant. But with the glasses, I can actually spot them quite easily which means they do something for sure. In my case the happiness vs. money was ratio was good enough.

Moving from sodium lights was a real problem for astronomers as narrow band filters were common and cheap, the LED lights are much harder to filter out due to having multiple peaks and the phosphors not being to a standard chemistry resulting in different lights having different frequency outputs.

Please never stop doing these kinds of videos. You are literally broadening my horizont. There are many things that are far out of my reach, knowledge wise, and you tap into them, but you also make me understand enough. It really is fun and exciting to watch videos like this. Not necessarily because of the topic, but because of how you are driving us in your bus through knowledge town. Sightseeing with you is fun, not boring. It's pleasant and exciting to learn more and to see the world a little bit through your eyes. (Or rather mind really lol). Thank you for putting this effort into your videos!

I don't always watch a Steve Mould video, but when I do, i learn way more than i intend to

I think spin is a lot less mysterious if you learn QFT. A half integer spin particles are just a natural consequence of a spinor field. You might ask, well how the spinor field is possible, it is weird and that's what I think too, but it's probably because we're just used to scalar and vector fields in our macroscopic life. Spinor field is weird to us, not weird to the universe.

Wow! Most science videos manage to teach you one amazing fact - this one just kept coming and coming with more and more answers to questions I've always wondered about. It's like a 6 month science course crammed into 20 minutes!

Fun fact, Robert Bunsen had an assistant with a speech impediment called Beaker.

Learned something today. Thank you.

EVERY, FREAKING, TIME, mostly, your videos are amazing, keep it up Steve!

Your sodium lamp isn’t pure sodium. There is at least a hint of neon in there for arc initiation, and I wonder if that is part of your spectrum impurity. Take another spectrograph of it when first cold lit, and I’ll bet that highlights the non-sodium component.

Oh, wow, you perfectly explained something that i totally flunked at/failed at explaining years ago to others. At the time i had known most of this, but, really struggled in expanding on this explanation, because, i struggled with condensing this information down into something bite size like this. Awesome video.

You explain stuff really well

It's kinda genius the subtle way you approached the relativistic nature of the electrons spin and the spin-orbit coupling. Kudos to you, Steve!

Incredible episode Steve, one of your best yet. I’ve seen a dozen efforts at explaining the black sulfur flame over the years and none have been as clear and complete as yours. Great job.

Wow! WOW! This is instantly one of my favourite videos online. So much good stuff - told without equivocating, yet just deep enough to get what you need and then move on. I'm going to suggest this to so many people. Thank you for an interesting, broad, focused (yes) and intellectually honest work of art and exposition.

Wow, I can't believe that I've never put two and two together, but I honestly didn't realize until now that sodium street lamps render color useless. It's not that I'm color-blind or anything; it's just a sort of conceptual understanding I've not stopped to consider enough for it to sink in. Always just thought of it as 'weird orange.' Amazing what you can miss! Thanks.

Such a good job !! I love this video it reminds me my college and atomistic classes that used to be boring ... That quality of pedalogical video is so unusual, this whole content deverse to be recommanded to all physics and chemistry students

15:24 Oh, come on!

I'm seriously impressed by how accurate, yet accessible, this video is. The relation between light spectrum and atomic orbitals is the heart of Quantum Mechanics; it's what drove its development historically and it's where the theory makes predictions that stumped the rest of physics. It's also the foundations of just about all of chemistry, material science, and the starting point of nuclear physics. I'd so far as to say that it's the most important development in the last 200 years of physics. And this madman casually explains it in 15min in a stunningly visual way.

You took this regular science experiment to a whole new level with the spectrum analyzer and the two goggles. Bravo!

I love how you shouted out your nephew :D

I'm pretty sure we used those same glasses in a class of mine for brazing copper pipe. Our teacher was very clear in stating these are NOT a pair of sunglasses and to use them on the road is VERY BAD. Those glasses are blocking the red/orange spectrum and apparently a couple students wore them out of class and rear ended a guy because they couldn't see their red brakelights.

the way you explained how certain waves of light is produced was far more understandable than what my high school physics class taught me, it actually kinda annoyed me how well you explained it

It’s good to know that many street lights, at least in the US, still have sodium lights but they also had two different kinds of sodium lights. High pressure and low pressure. High pressure produced light on a broader spectrum and were thus used as grow lights and still are. At least in areas where electricity is affordable.

the analogy with the re-emitted photons reminded me that there are glass lenses made in a way that has a black spot / shadow in the center due to the change of angle from where light enters, and towards the exit

Disney used "amber screen" in Mary Poppins , that predated green/blue screen special effects, back in the 1950s . It used sodium lamps. And it is superior in many ways to green screen and blue screen. It's even possible to do transparent things like water and fine hair, which has proved very difficult to do in green screen.

I just saw Brainiac75's video about the sodium lamp and the CRI bit lol The science youtubers syncing up once more.

To filter out the sodium yellow we used to use pieces of cobalt glass in the lab. But the use case really was just to be able to see the colour potassium salts give to a flame in the presence of miniscule amounts of sodium (like, always) which would outshine the potassium. Cool to see, after so many years, that there is actually a real use case for this, although not with cobalt glass.

This felt like such a knowledge-dense video. Firing on all cylinders!